Dr Collins first found fame identifying the gene that caused cystic fibrosis in 1989, then went on to discover the gene for neurofibromatosis in 1990 and a gene for Huntingdon's Disease in 1993. Now he heads the publicly funded National Human Genome Research Institute in Washington.

"Everything will be divided into the era before we had this information and the era after we had it," Collins predicts.

Dr Collins was appointed director of the NHGRI in 1993, following in the footsteps of DNA pioneer Dr James Watson. Now his laboratory is exploring the molecular genetics of breast cancer, prostate cancer and adult-onset diabetes among other diseases.

James Watson

It is nearly 50 years since James Watson and Francis Crick made what many scientists previously believed was the most important discovery of the 20th century: the structure of DNA.

At 72, the brash American who wrote a controversial bestseller, The Double Helix, about his Nobel prize-winning discovery, is still at the forefront of his field.

In 1992 internal politics pushed him from the director's seat of the US branch of the Human Genome Project. Now, Watson is president of Cold Spring Harbor laboratory in New York, where he turned to research into cancer almost 30 years ago. The first suggestion that DNA might have something to do with inheritance was made in 1944. Watson and Crick saw a pattern of evidence that others around them had missed. Watson has always said he was lucky that the others missed the vital clues.

Watson, one of whose sons was born with a severe learning disability, also believes parents have a moral responsibility to make sure their babies are born as healthy as possible.

William Haseltine

Multimillionaire socialite and brilliant scientist Dr William A Haseltine is chief executive of the private company, Human Genome Sciences, based in Rockville, Maryland, US. The pharmaceutical company uses genome data to develop new drug treatments and demands royalties from anyone who works on the gene, a move which has attracted criticism from fellow scientists. Among the genes patented by this company is that for CCR5, the receptor used by the Aids virus to enter human cells.

In 1982 Haseltine came up with the then controversial hypothesis that Aids was caused by a retrovirus. Greeted with scepticism at the time, he was later proved to be correct.

In 1992 he went into partnership with Craig Venter to sequence the human genome. Personality clashes led them to separate in 1997.

William French Anderson

Dr William French Anderson Jr, of the University of Southern California in Los Angeles, foresees a day when genetic therapy will be used to treat not only the living but those who have not yet been born. He hopes to get approval within the next few years to use gene therapy on a foetus that has been diagnosed with a deadly inherited disease.

"Gene therapy will revolutionise the practice of medicine. In 20 years, every major disease will have gene therapy as a treatment option," Anderson said.

In 1979, Anderson led a team of scientists with the National Institutes of Health in curing a genetic flaw in the cells of mice. By 1990, his laboratory had performed the first gene therapy experiment on a 4-year-old child with a rare genetic disease that prevents babies from developing their own immune systems.

Since Anderson's first experiment, more than 3,000 people have received gene therapy as part of clinical trials worldwide.